The present invention relates to processes and equipment for embossing and applying adhesive to thin film webs.
Three-dimensional sheet materials which include a thin layer of pressure-sensitive adhesive protected from inadvertent contact, as well as methods and apparatus for manufacturing them, have been developed and are described in detail in commonly-assigned U.S. Pat. No. 5,662,758, issued Sep. 2, 1997 to Hamilton and McGuire, entitled xe2x80x9cComposite Material Releasably Sealable to a Target Surface When Pressed Thereagainst and Method of Makingxe2x80x9d, U.S. Pat. No. 5,871,607, issued Feb. 16, 1999 to Hamilton and McGuire, entitled xe2x80x9cMaterial Having A Substance Protected by Deformable Standoffs and Method of Makingxe2x80x9d. U.S. Pat. No. 6,254,965 issued Jul. 3, 2001 to McGuire, Tweddell, and Hamilton, entitled xe2x80x9cThree-Dimensional, Nesting-Resistant Sheet Materials and Method and Apparatus for Making Samexe2x80x9d, and U.S. Pat. No. 6,194,062. issued Feb. 27, 2001 to Hamilton and McGuire, entitled xe2x80x9cImproved Storage Wrap Materialsxe2x80x9d, all of which are hereby incorporated herein by reference.
While the processes and equipment for manufacturing such materials described in these applications/patents are suitable for manufacturing such materials on a comparatively small scale, the nature of the processes and equipment have been found to be rate-limiting by design. Said differently, the maximum speed at which such processes and equipment can be operated to produce such materials is limited by the size or weight of moving components, the rate at which heat can be applied to deformable substrate materials, the rate at which forces can be imparted to the substrate to deform it into the desired configuration, and/or the rate at which adhesive can be applied to the substrate and/or intermediate apparatus elements. The speed at which such processes and apparatus can be operated is a major factor in the economics of producing such materials on a commercial scale.
Accordingly, it would be desirable to provide a process and apparatus suitable for forming such three-dimensional sheet materials and applying adhesive at high speed.
The present invention provides a process which in a preferred embodiment includes the steps of. (a) applying a hot melt adhesive to a heated roll rotating at an initial tangential speed; (b) milling the adhesive to a reduced thickness and accelerating said adhesive through a series of metering gaps between a plurality of adjacent heated glue rolls; (c) applying the adhesive to a conformable glue application roll rotating at a tangential line speed which is higher than the initial tangential speed; (d) applying the adhesive to a first patterned embossing roll which is engaged with a second patterned embossing roll having a complementary pattern to the first embossing roll, the embossing rolls being heated; (e) passing a web of sheet material between the first and second embossing rolls at the tangential line speed to simultaneously emboss the web and apply the adhesive to the web, such that the adhesive forms an adhesive pattern between embossments; (f) transferring the web from the second embossing roll to the first embossing roll; (g) stripping the web from the first embossing roll; and (h) cooling the web.